The diamond should be in the same line as moderator's name. Adding a non-breaking space after the name, and removing
margin-left: 3px; CSS rule from
.mod-flair fixes that.
Reproduced in Chrome, but not in Firefox.
On this particular comment it happens only when logged in, because
the space reserved for the comment vote and flag buttons reduces the width of the comment text column by a few pixels. Those buttons are not present if you're not logged in, leaving a bit more room for the comments themselves. Carefully tweaking the comment text length (or column width) using the dev tools can still trigger it.
(as pointed out in comments by Ilmari Karonen)